In some communication systems, it is necessary to send data along with a signaling channel. For example, in inband signaling systems, a message channel is created based on inband signaling information provided with the signaling channel.
In a typical inband signaling system, the system uses the least significant bit (LSB) of every Mth sample of a signaling channel. In most cases, the degradation resulting from the use of the collected LSBs is not significant. The collected LSBs are concatenated to create an inband message channel which can be used by the inband signaling system for various purposes, including to facilitate tandem free operation (TFO) between two or more devices in the system.
One problem with inband signaling systems is that devices in the system must be synchronized in order to decode the inband signals. GSM specifications, for example, define the synchronization and resynchronization patterns and suggests attempting resynchronization in +/− one frame. Prior to synchronization, there are M possible signaling channels, where M−1 is the total number of samples occurring between each inband signal bit (described below). Until the system can determine which of the M possible signaling channels is the correct one, the devices will not be synchronized. In prior art inband signaling systems, it can take considerable time to achieve synchronization since all of the M possible signaling channels have to be collected and compared to a synchronization pattern before synchronization is achieved. However, it is desirable to achieve synchronization as quickly as possible. Therefore, there is a need for techniques to speed up the synchronization or re resynchronization process.